In an injection molding apparatus having a plurality of valve-pin gated hot runner nozzles for injecting melt into a plurality of mold cavities, proper alignment between the moving components is desired in order to maximize the lifetime of the components and produce high quality molded parts.
Typically, prior art valve-gated nozzles include reciprocating valve pins, which retract to open the mold gates and extend to close the mold gates. In this type of arrangement, the valve pin is typically un-guided during the entirety of the opening and closing phases of the injection cycle.
Several known valve-gated nozzles include continuously guided valve pins, which reduce wear on the valve pin and mold gate. These nozzles are typically limited to molding articles having a hole, such as a compact disc, for example. U.S. Pat. No. 5,423,672 to Gordon discloses a valve-gated nozzle for molding products having a hole.
In some valve gated nozzle systems, it is common for a blush mark to appear on the molded part, opposite the gate. The blush mark occurs as a result of the flow patterns in the melt, when the melt enters the mold cavity at such a high pressure in a concentrated stream it hits the cold back wall forming flow lines that appear on the part as what is commonly termed a blush mark. This may be unacceptable in molded parts that have an aesthetic requirement,especially with high gloss, show surfaces, and with surfaces that are painted, chrome plated or similarly processed after molding.
Thus, a valve pin for an injection molding system that obviates or mitigates at least one of the above-noted concerns is desirable.